The present invention relates to a coating machine, especially a chocolate-coating machine.
Chocolate-coating machines serve, as is known, to coat articles, such as chocolates, bars, biscuits or cakes, with chocolate either partially or completely. In general, the article runs through a thick curtain of chocolate which covers the surface and the vertical sides. A base wall can also be present to bring the chocolate to the bases of the articles. The articles are thus flooded by the liquid chocolate. A blow-off device and a shaking device provided underneath part of the grating belt ensure removal of excess liquid chocolate from the article, whilst leaving the desired coating of chocolate. As a rule, the blowoff device as well as the shaking device can be regulated in order to adapt them to the performance requirement and the desired wall thickness of the coating, respectively. It depends on the blow-off device on the one hand and the shaking device on the other hand whether all articles, seen over the entire working width of the grating belt of a coating machine and also in running direction, are always coated in the same manner, thus have a chocolate component which is constant in terms of quantity. The maintenance of this condition is extremely important for reasons of quality and costs, because the coating is usually the most expensive part of the end product produced from the article.
In a known chocolate-coating machine of the above-described kind, a shaking device is arranged in a region below the upper run of the grating belt and includes a shaker grating which is mounted in fixedly located side cheeks to be limitedly pivotable about an axle arranged transversely to the running direction of the belt. The grating consists of a plurality of longitudinal rods, thus rods extending in running direction of the belt, which are arranged at spacings and parallel to each other over the working width of the belt. During circulation the belt comes into contact with the surface of these longitudinal rods. The longitudinal rods are mostly mounted on two transverse rods, which serve to keep the longitudinal rods at a spacing and to connect them to the grating. The transverse rods lie underneath the plane formed by the surface of the longitudinal rods, so that the underside of the belt does not come into contact with the transverse rods. When operating with such a grating, an appreciable proportion of the articles, which are coated while lying on the belt in rows one beside the other, will be disposed in the region of the longitudinal rods. Some chocolate in the base region is wiped off any articles moving on the belt above the longitudinal rods. Such articles thereby receive a many cases, unsightly hollow spaces additionally appear at the bases of the articles. A further appreciable disadvantage has resulted in the course of time by the fact that coating machines are increasing in width. Whilst the maximum working widths were once 1000 to 1200 millimetres, the width nowadays is about 2000 millimetres. These large working widths require reinforcement of the grating, which means a disadvantageous increase in weight. Moreover, there may be increased wear of the shaker wheels which set the grating into a vibration with substantial vertical component about the horizontal axle. There can also be resonant oscillation of the grating in the case of large working widths, especially in the middle region with respect to the running direction of the belt, so that the shaken-off quantity of chocolate in the middle region of the belt is different from that in the side regions.
In order to counteract these disadvantages, it has been attempted to stiffen the grating by additional transverse rods, which were loaded onto the s aced longitudinal rods and which had the form of round rods of steel. Since these additional transverse rods were arranged on the longitudinal rods to be protruding upwardly, the underside of the belt came into contact only with the additional transverse rods. This resulted in a uniform appearance of the base of the articles. However, the weight of the grating was thereby increased and the problems of wear and resonant oscillations also increased. A high weight or a large mass of the grating also has a disadvantageous effect on the usable shaking frequency. Frequencies in the order of 300 strokes per minute are used. An increase in the rotational speed of the shaker wheels causes them to jump over individual teeth of the shaker pins arranged at the grating.